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View Full Version : F13 f/d choice, advice needed.


John
29-12-09, 03:43 PM
When rebuilding my sport, i'll be using an F13 box, but what would be the best F/D ratio to go for and why?

What will i acheive if i fit 4.53? Crap accelleration, higher top speed?

I have a 4.18 in an f10, i'm reckoning this would be the better option? Discuss. :)
Morton
29-12-09, 03:51 PM
4.53 is your best acceleration lowest top speed 4.18 is higher top speed lower acceleration you best just sticking to something in between for a road car as 4.53 will give you lots off wheel spin and great acceleration but will only acheive about 90mph ... some correct me if im wrong.
SR-Rally
29-12-09, 04:00 PM
i have 4:53 fitted to my rally car and its brilliant for the backroads and acceleration but it revs about 4,000 rpm at 60mph which would drive me nuts for an everyday car. the top speed is over 90mph ;)
Morton
29-12-09, 04:04 PM
nnot so bad then .. if you can live with noise and wheelspin and feeling like your in a rally car:) 4.53 other than that for every day id pick something else
brucer
29-12-09, 05:06 PM
i always wanted to fit a 4.18 into my f13 but didnt want to lose out on top end, so stuck with the standard 3.74 as it was a road car.

edit: if it was in a low powered car then i would change it, but as you said "sport" i presume 1300 twin carbs etc?.
boffer8
29-12-09, 05:41 PM
i have an F13 with a 4.18 in it and find that for scatters and night rallys/enduro events its spot on and doesnt pain you too much when your cruising on the motor way like i had to do a few times when going to angelsey (from leeds)
Stuart
29-12-09, 06:01 PM
iirc with Dans going from 3.94 to 4.18 it lost approx 5% top end down to 125ish at 7.7something K his rev limit was on 15" wheels.

IMHO not the end of the world.
Personally the 4.18 is the best of both worlds for day to day use/living with vs fun when used in anger
John
29-12-09, 08:28 PM
iirc with Dans going from 3.94 to 4.18 it lost approx 5% top end down to 125ish at 7.7something K his rev limit was on 15" wheels.

IMHO not the end of the world.
Personally the 4.18 is the best of both worlds for day to day use/living with vs fun when used in anger

Ta Stuart, 4.18 it is then!
tom reid
29-12-09, 08:36 PM
As Stuart says 4.18 is the one to have, with std cr cartridge.
1st 32mph
2nd 53mph
3rd 79mph
4th 101mph
5th 127mph
max revs was 7k
You can always put a wide ratio gear on 5th for more relaxed cruising.
John
29-12-09, 08:41 PM
As Stuart says 4.18 is the one to have, with std cr cartridge.
1st 32mph
2nd 53mph
3rd 79mph
4th 101mph
5th 127mph
max revs was 7k
You can always put a wide ratio gear on 5th for more relaxed cruising.

Cool, The f13cr i have atm is 3.74iirc, i'll strip the 4.18 out of the f10.
jimbob-mcgrew
31-12-09, 01:39 AM
Cool, The f13cr i have atm is 3.74iirc, i'll strip the 4.18 out of the f10.

^ that'll be a nice blend :thumb: when pulling away youll prob have to go v.quickly into second but it should be nice after that